Really better off waiting on 4K until every thing like HDMI 2.0 and H.265 codec is ironed out. Large 4K sets are around $7,000-$15,000, way above your budget. There probably won't be much 4K content until 2015 anyway. If you need a display right now, I would grab one on the cheap Panasonic plasmas like the 65" Panasonic S64 for $1500 and waiting it out.
If you're thinking about buying a Samsung, at least wait a year until HDMI 2.0 arrives, then you can get compatibility fixes via Evolution kits. This is what I am planning as well since I've decided to go with the Samsung plasma.